Dear Keld,

See ?predict.lm and its examples.

HTH,

Jorge


On Wed, Jul 2, 2008 at 9:40 PM, Keld Jørn Simonsen <keld@dkuug.dk> wrote:

> Hi
>
> I have a problem with lm and predict
>
> I have
>
> us
>  [1]  2789.53  3128.43  3255.03  3536.68  3933.18  4220.25  4462.83 4739.48
>  [9]  5103.75  5484.35  5803.08  5995.93  6337.75  6657.40  7072.23 7397.65
> [17]  7816.83  8304.33  8746.98  9268.43  9816.98 10127.95 10469.60
> 10960.75
> [25] 11685.93 12433.93 13194.70 13843.83
>
>
>  us.p
>  [1] 227.62 229.92 232.13 234.25 236.31 238.42 240.59 242.75 244.97 247.29
> [11] 250.05 253.39 256.78 260.15 263.33 266.46 269.58 272.82 276.02 279.20
> [21] 282.31 285.25 288.10 290.85 293.53 296.26 299.08 301.97
>
>  us.l = lm(log(us) ~ log(us.p))
> > predict(us.l,n.ahead=5)
>       1        2        3        4        5        6        7        8
> 8.079754 8.131908 8.181531 8.228692 8.274111 8.320224 8.367224 8.413588
>       9       10       11       12       13       14       15       16
> 8.460813 8.509709 8.567285 8.636117 8.705057 8.772694 8.835719 8.897015
>      17       18       19       20       21       22       23       24
> 8.957402 9.019376 9.079867 9.139289 9.196752 9.250495 9.302067 9.351347
>      25       26       27       28
> 9.398927 9.446950 9.496094 9.545979
>
>
> Why does predict not give me any predictions? The result of predict() is
> same lenght (28) as the us and us.p variables.
>
> best regards
> keld
>
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